Look at it from around 3,500 feet above Tangier Island, in the cleaned-out sunlight that follows a snowstorm. The estuary is silver and overwhelming; the only man-made things are just flecks in the foreground. Or follow the water upstream into Virginia, and hover a mile and a half above the Seven Bends of the Shenandoah River's North Fork. The scene below appears primeval: Nature is still working on an errand as old as the Blue Ridge, making a loopy stream run straight.

But the images also bear witness to the bay's vulnerability and the fragility of its future. That's because nearly all of the shots show signs of human intrusion: our cows fouling a country stream, our nets trapping fish, our homes and bright-blue swimming pools colonizing a neck of bayside land. As the bay watershed spreads, we have spread with it and tried to make it work for us -- as a seafood pantry, as a real-estate amenity, as a playground, as a gutter.

The bay has been around for more than 10,000 years, formed when melting glaciers drowned a long stretch of the Susquehanna River Valley. The Chesapeake watershed stretches over 64,000 square miles -- its arms are big rivers such as the Susquehanna, the Potomac and the James, and its spider web fingers extend into sweaty tidal swamps, out to the hard-rock folds of Appalachia and up to the cold woods near Cooperstown, N.Y.

For centuries, these waters mixed with Atlantic Ocean backwash to make a brackish estuary and an ecological superconductor. The Chesapeake was alive with crabs, sturgeon and rockfish. Oysters grew on oysters, in reefs so big they broke the surface of the water. The bay's bounty, which helped sustain Native Americans for centuries, seemed endless.

Then: the rest of us.

After Europeans arrived, their axes took out the trees that served as a natural water filter. Their ships scraped away the bay's oysters. Their plows disturbed the earth, and then rain-water carried that earth downstream. Bladensburg was originally a deepwater port, but by 1830 the Anacostia River was heavy with silt for big ships.

Today's Chesapeake serves as a kind of living memory of those sins, and a few that we're still cooking up. More than 16.5 million people now inhabit the Chesapeake watershed. Fertilizer from our lawns, manure from our farms and treated sewage from our cities help create oxygen-starved "dead zones" downstream in the bay. Toxic compounds from urban areas have been blamed for tumors on fish in the Anacostia and South rivers. And mysterious (but assuredly man-made) pollutants are creating other problems: Male bass in the Potomac are producing eggs, and fish in the Shenandoah die in droves every spring.

"Our tools are better than our wisdom, and that's a tough thing to swallow," says John Page Williams, a senior naturalist at the Chesapeake Bay Foundation.

Cameron Davidson has been shooting the Chesapeake since 1980, when he went up in a Bell JetRanger on assignment for National Geographic to snap photos of great blue herons living in the marshes near the Patuxent River in Southern Maryland. He was hooked, both on aerial shooting and on the Chesapeake as a subject. "I absolutely fell in love," Davidson says.

The attraction is partly artistic: At a high-enough level, the earth is abstract expressionism. In these shots, Davidson found lazy bends and fractal branching, plus the straight lines and corners we build alongside them.

But he is also delivering a message. Hovering in the air, Davidson could capture both the bay and its antagonists in the same long-range shot: the polluted Patapsco River and Baltimore County's Sparrows Point steel mill; the Elk River and a packed-in trailer park at its edge. "I can send this to governors," he says, and make the complicated question of what's killing the bay seem simpler.

Some fear that eventually the bay may be pushed beyond an invisible point of no return -- that even if we finally muster the will to mend our ways, we'll find that the crabs, oysters and underwater grasses are so depleted that they can't return.

For now, though, there is still life in the Chesapeake and hope here on land. The hope: a promise of greater urgency from the federal government in overseeing the 25-year-old effort to clean up the bay, a program with middling results. Already, state and local initiatives have managed to bring the decimated rockfish population nearly all the way back from the brink. The blue crab may be on the verge of a revival, too.

And the life shows in Davidson's photos of the bay in spring. Flying low over the north shore of the James River near James-town -- near the very spot where our long, dirty history with the Chesapeake began -- he caught a marsh rebounding, re-creating itself, after winter. The water is olive. The plants are emerald. Green, the color of new life, is the entire palette.

From 300 feet, at least, the place looks like it's never been touched.

David Fahrenthold covers the environment for The Post. He can be reached at fahrenthold@washpost.com.